fix(tmux): isolate sessions on a dedicated socket + raise pane nofile limit (fixes new-session crash after tmux upgrade) (#96)

* fix: isolate codeman tmux sessions

* fix(tmux): unify all sessions onto a single dedicated socket

Remove the per-session `tmuxSocket` field that recorded which tmux server
each session lived on (default vs the `codeman` socket). That field was a
persisted cache of physical reality and could drift — causing live sessions
to be wrongly marked dead ("tab shows no session found") and spawning
duplicate "Restored:" tabs.

All Codeman sessions now live on one process-wide socket (`tmux -L codeman`,
overridable via CODEMAN_TMUX_SOCKET), exposed via TmuxManager.muxSocket on
the TerminalMultiplexer interface. reconcileSessions() collapses from a
multi-socket scan (locate / re-pin / cross-socket dedup) to a single
`list-panes` query. loadSessions() strips the obsolete field from on-disk
records so it stops being written back.

Also fix two sibling bare-`tmux` call sites the unification would otherwise
leave broken (same #80 regression class — bare tmux hits the user's default
server and never finds a session on the codeman socket):
- session.ts queryTmuxWindowSize(): add `-L <socket>` (was silently falling
  back to 120x40 on re-attach, losing scrollback)
- session-routes.ts send-key (Shift+Enter / Ctrl+Enter newline): route
  through ctx.mux.muxSocket

SSH chooser scripts (tmux-manager.sh, tmux-chooser.sh) route every tmux call
through `tmux -L $CODEMAN_TMUX_SOCKET`, matching the TS default.

---------

Co-authored-by: Teigen <teigen@TeigendeMac-mini.local>

scripts/tmux-chooser.sh

@@ -32,6 +32,13 @@ set -e
 CODEMAN_STATE="$HOME/.codeman/state.json"
 CODEMAN_SESSIONS="$HOME/.codeman/mux-sessions.json"
 
+# Dedicated tmux socket all Codeman sessions live on. MUST match
+# DEFAULT_CODEMAN_TMUX_SOCKET / CODEMAN_TMUX_SOCKET in src/tmux-manager.ts —
+# otherwise list-sessions would enumerate the user's default tmux server
+# (missing the real Codeman sessions, surfacing unrelated ones).
+CODEMAN_TMUX_SOCKET="${CODEMAN_TMUX_SOCKET:-codeman}"
+TMUX_CMD=(tmux -L "$CODEMAN_TMUX_SOCKET")
+
 
 # iPhone 17 Pro portrait width (conservative)
 MAX_WIDTH=44
@@ -286,7 +293,7 @@ parse_sessions() {
 
         # Get PID from tmux
         local pid
-        pid=$(tmux display-message -t "$session_name" -p '#{pane_pid}' 2>/dev/null || echo "0")
+        pid=$("${TMUX_CMD[@]}" display-message -t "$session_name" -p '#{pane_pid}' 2>/dev/null || echo "0")
 
         SESSION_PIDS+=("$pid")
         MUX_NAMES+=("$session_name")
@@ -314,7 +321,7 @@ parse_sessions() {
         fi
 
         i=$((i + 1))
-    done < <(tmux list-sessions 2>/dev/null || true)
+    done < <("${TMUX_CMD[@]}" list-sessions 2>/dev/null || true)
 }
 
 # ============================================================================
@@ -462,7 +469,7 @@ attach_session() {
     echo -e "${D}(Ctrl+B D to detach)${R}"
     sleep 0.3
 
-    tmux attach-session -t "$mux_name"
+    "${TMUX_CMD[@]}" attach-session -t "$mux_name"
 
     return 0
 }

scripts/tmux-manager.sh

@@ -20,6 +20,13 @@ REVERSE='\033[7m'
 # Use the same path as codeman (src/tmux-manager.ts)
 SESSIONS_FILE="${HOME}/.codeman/mux-sessions.json"
 
+# Dedicated tmux socket all Codeman sessions live on. MUST match
+# DEFAULT_CODEMAN_TMUX_SOCKET / CODEMAN_TMUX_SOCKET in src/tmux-manager.ts —
+# otherwise this script would talk to the user's default tmux server and never
+# see (or could mis-target) Codeman's sessions.
+CODEMAN_TMUX_SOCKET="${CODEMAN_TMUX_SOCKET:-codeman}"
+TMUX_CMD=(tmux -L "$CODEMAN_TMUX_SOCKET")
+
 
 # Cached data
 CACHED_JSON=""
@@ -92,7 +99,7 @@ declare -A ALIVE_CACHE
 check_alive() {
     local mux_name=$1
     if [[ -z "${ALIVE_CACHE[$mux_name]+x}" ]]; then
-        if tmux has-session -t "$mux_name" 2>/dev/null; then
+        if "${TMUX_CMD[@]}" has-session -t "$mux_name" 2>/dev/null; then
             ALIVE_CACHE[$mux_name]=1
         else
             ALIVE_CACHE[$mux_name]=0
@@ -111,8 +118,10 @@ kill_session() {
     local mux_name=$(get_session_field $idx "muxName")
     local pid=$(get_session_field $idx "pid")
 
-    # SAFETY: Never kill own tmux session
+    # SAFETY: Never kill own tmux session. Queried on the Codeman socket; if run
-    local current_session=$(tmux display-message -p '#{session_name}' 2>/dev/null || echo "")
+    # from a session on a different socket this returns empty (no match), which
+    # is fine — you can't be "inside" a Codeman-socket session you didn't attach to.
+    local current_session=$("${TMUX_CMD[@]}" display-message -p '#{session_name}' 2>/dev/null || echo "")
     if [[ -n "$current_session" && "$mux_name" == "$current_session" ]]; then
         echo -e "${RED}BLOCKED: Cannot kill own tmux session: $mux_name${NC}"
         return 1
@@ -120,7 +129,7 @@ kill_session() {
 
     pkill -TERM -P $pid 2>/dev/null
     kill -TERM -$pid 2>/dev/null
-    tmux kill-session -t "$mux_name" 2>/dev/null
+    "${TMUX_CMD[@]}" kill-session -t "$mux_name" 2>/dev/null
     kill -KILL $pid 2>/dev/null
 
     # Remove from JSON
@@ -345,7 +354,7 @@ interactive_menu() {
                         clear
                         echo -e "${CYAN}Attaching... (Ctrl+B D to detach)${NC}"
                         sleep 0.3
-                        tmux attach-session -t "$mux_name"
+                        "${TMUX_CMD[@]}" attach-session -t "$mux_name"
                         tput civis
                         need_full_redraw=1
                         force_refresh
@@ -474,7 +483,7 @@ main() {
             [[ -z "${2:-}" ]] && { echo "Usage: $0 attach <N>"; exit 1; }
             force_refresh
             local mux_name=$(get_session_field $(($2-1)) "muxName")
-            check_alive "$mux_name" && tmux attach-session -t "$mux_name" || echo "Session dead or not found"
+            check_alive "$mux_name" && "${TMUX_CMD[@]}" attach-session -t "$mux_name" || echo "Session dead or not found"
             ;;
         kill)
             [[ -z "${2:-}" ]] && { echo "Usage: $0 kill <N|N,M|N-M>"; exit 1; }
@@ -492,8 +501,8 @@ main() {
             ;;
         kill-all)
             force_refresh
-            # SAFETY: Never kill own tmux session
+            # SAFETY: Never kill own tmux session (queried on the Codeman socket)
-            local current_session=$(tmux display-message -p '#{session_name}' 2>/dev/null || echo "")
+            local current_session=$("${TMUX_CMD[@]}" display-message -p '#{session_name}' 2>/dev/null || echo "")
             local killed=0
             for ((i=CACHED_COUNT-1; i>=0; i--)); do
                 local mux_name=$(get_session_field $i "muxName")

src/mux-interface.ts

@@ -98,6 +98,9 @@ export interface TerminalMultiplexer extends EventEmitter {
   /** Which backend this instance uses */
   readonly backend: 'tmux';
 
+  /** The dedicated tmux socket name all sessions live on (e.g. "codeman"). */
+  readonly muxSocket: string;
+
   // ========== Lifecycle ==========
 
   /**

src/session.ts

@@ -133,15 +133,22 @@ const TMUX_DISPLAY_TIMEOUT_MS = 2000;
  * (tmux dead, muxName unknown, malformed output) — caller never has to
  * differentiate "tmux unreachable" from "size 120x40".
  *
+ * `socket` MUST be the same dedicated socket the session lives on (`mux.muxSocket`);
+ * querying the default server would never find the session and silently fall back.
+ *
  * Argv form (execFileSync, not execSync) keeps `muxName` out of any shell so
  * a hostile session name can't inject options.
  */
-export function queryTmuxWindowSize(muxName: string): { cols: number; rows: number } {
+export function queryTmuxWindowSize(muxName: string, socket: string): { cols: number; rows: number } {
   try {
-    const sizeStr = execFileSync('tmux', ['display', '-t', muxName, '-p', '#{window_width} #{window_height}'], {
+    const sizeStr = execFileSync(
-      timeout: TMUX_DISPLAY_TIMEOUT_MS,
+      'tmux',
-      encoding: 'utf8',
+      ['-L', socket, 'display', '-t', muxName, '-p', '#{window_width} #{window_height}'],
-    }).trim();
+      {
+        timeout: TMUX_DISPLAY_TIMEOUT_MS,
+        encoding: 'utf8',
+      }
+    ).trim();
     const [w, h] = sizeStr.split(' ').map(Number);
     if (w > 0 && h > 0) {
       return { cols: w, rows: h };
@@ -978,7 +985,7 @@ export class Session extends EventEmitter {
 
     // Attach to the mux session via PTY
     // Query existing tmux window size so re-attach matches (avoids flicker from 120x40 default)
-    const { cols: ptyCols, rows: ptyRows } = queryTmuxWindowSize(this._muxSession!.muxName);
+    const { cols: ptyCols, rows: ptyRows } = queryTmuxWindowSize(this._muxSession!.muxName, mux.muxSocket);
     try {
       this.ptyProcess = pty.spawn(mux.getAttachCommand(), mux.getAttachArgs(this._muxSession!.muxName), {
         name: 'xterm-256color',

src/tmux-manager.ts

@@ -71,6 +71,9 @@ const GRACEFUL_SHUTDOWN_WAIT_MS = 100;
 /** Default stats collection interval (2 seconds) */
 const DEFAULT_STATS_INTERVAL_MS = 2000;
 
+/** Claude Code native macOS recommendation for avoiding low nofile startup failures. */
+export const CLAUDE_CODE_NOFILE_LIMIT = 2147483646;
+
 /**
  * SAFETY: Test mode detection.
  * When running under vitest (VITEST env var is set automatically),
@@ -98,6 +101,12 @@ const LEGACY_MUX_NAME_PATTERN = /^claudeman-[a-f0-9-]+$/;
 /** Regex to validate tmux pane targets (e.g., "%0", "%1", "0", "1") */
 const SAFE_PANE_TARGET_PATTERN = /^(%\d+|\d+)$/;
 
+/** Dedicated tmux socket for new Codeman-owned sessions. */
+const DEFAULT_CODEMAN_TMUX_SOCKET = 'codeman';
+
+/** Regex to validate tmux socket names passed to `tmux -L`. */
+const SAFE_TMUX_SOCKET_PATTERN = /^[a-zA-Z0-9_.-]+$/;
+
 /**
  * Separator used in `tmux list-panes -F` output between session name and pid.
  *
@@ -114,6 +123,19 @@ const PANE_LIST_SEP = '|';
 /** Format string for `tmux list-panes -F`. Keep in sync with {@link parsePaneList}. */
 const PANE_LIST_FORMAT = `#{session_name}${PANE_LIST_SEP}#{pane_pid}`;
 
+/**
+ * 构建 pane 启动前的 nofile 修复命令。
+ *
+ * macOS launchd/tmux 组合有时会让 pane 继承 256 的 soft nofile；
+ * 新版 Claude Code 会在这种环境下直接退出。这里避免使用 $变量
+ * 或命令替换，因为 fullCmd 目前经由双引号 bash -c 传递，外层
+ * shell 会提前展开它们。
+ */
+export function buildNofileLimitCommand(targetLimit = CLAUDE_CODE_NOFILE_LIMIT): string {
+  const safeLimit = Number.isSafeInteger(targetLimit) && targetLimit > 0 ? targetLimit : CLAUDE_CODE_NOFILE_LIMIT;
+  return `ulimit -Sn ${safeLimit} 2>/dev/null || ulimit -n ${safeLimit} 2>/dev/null || true`;
+}
+
 /**
  * Parse the output of `tmux list-panes -a -F '#{session_name}|#{pane_pid}'`
  * into a Map of session-name → pane pid. Exported for unit testing.
@@ -161,6 +183,31 @@ function isValidPath(path: string): boolean {
   return SAFE_PATH_PATTERN.test(path);
 }
 
+// ===========================================================================
+// Single-socket architecture: ALL Codeman sessions live on one dedicated tmux
+// socket (`tmux -L codeman`), isolated from the user's default tmux server.
+// The socket name is a process-wide constant (env-overridable for test/multi-
+// instance isolation) — it is never stored per-session, so it cannot drift.
+// ===========================================================================
+
+/**
+ * Resolve the process-wide Codeman tmux socket name. Always returns a valid
+ * name: `CODEMAN_TMUX_SOCKET` env override if safe, else the built-in default.
+ */
+function resolveConfiguredTmuxSocket(): string {
+  const raw = process.env.CODEMAN_TMUX_SOCKET ?? DEFAULT_CODEMAN_TMUX_SOCKET;
+  if (!SAFE_TMUX_SOCKET_PATTERN.test(raw)) {
+    console.warn(`[TmuxManager] Ignoring invalid CODEMAN_TMUX_SOCKET: ${JSON.stringify(raw)}`);
+    return DEFAULT_CODEMAN_TMUX_SOCKET;
+  }
+  return raw;
+}
+
+/** Build the `tmux -L <socket>` command prefix. Socket name is shell-escaped. */
+function tmuxCommand(socket: string): string {
+  return `tmux -L ${shellescape(socket)}`;
+}
+
 /**
  * Build Claude CLI permission flags for the tmux command string.
  * Validates allowedTools to prevent command injection.
@@ -248,7 +295,7 @@ function buildSpawnCommand(options: {
  * Set sensitive environment variables on a tmux session via setenv.
  * These are inherited by panes but not visible in ps output or tmux history.
  */
-function setOpenCodeEnvVars(muxName: string): void {
+function setOpenCodeEnvVars(tmuxCmd: string, muxName: string): void {
   const sensitiveVars = ['ANTHROPIC_API_KEY', 'OPENAI_API_KEY', 'GOOGLE_API_KEY'];
   for (const key of sensitiveVars) {
     const val = process.env[key];
@@ -256,7 +303,7 @@ function setOpenCodeEnvVars(muxName: string): void {
       // Shell-escape: wrap in single quotes, escape any inner single quotes
       const escaped = val.replace(/'/g, "'\\''");
       try {
-        execSync(`tmux setenv -t '${muxName}' ${key} '${escaped}'`, {
+        execSync(`${tmuxCmd} setenv -t '${muxName}' ${key} '${escaped}'`, {
           encoding: 'utf8',
           timeout: EXEC_TIMEOUT_MS,
           stdio: ['pipe', 'pipe', 'pipe'],
@@ -272,7 +319,7 @@ function setOpenCodeEnvVars(muxName: string): void {
  * Set OPENCODE_CONFIG_CONTENT on a tmux session via setenv.
  * Uses tmux setenv to avoid shell metacharacter injection from user-supplied JSON.
  */
-function setOpenCodeConfigContent(muxName: string, config?: OpenCodeConfig): void {
+function setOpenCodeConfigContent(tmuxCmd: string, muxName: string, config?: OpenCodeConfig): void {
   if (!config) return;
 
   let jsonContent: string | undefined;
@@ -303,7 +350,7 @@ function setOpenCodeConfigContent(muxName: string, config?: OpenCodeConfig): voi
   if (jsonContent) {
     const escaped = jsonContent.replace(/'/g, "'\\''");
     try {
-      execSync(`tmux setenv -t '${muxName}' OPENCODE_CONFIG_CONTENT '${escaped}'`, {
+      execSync(`${tmuxCmd} setenv -t '${muxName}' OPENCODE_CONFIG_CONTENT '${escaped}'`, {
         encoding: 'utf8',
         timeout: EXEC_TIMEOUT_MS,
         stdio: ['pipe', 'pipe', 'pipe'],
@@ -336,6 +383,7 @@ function setOpenCodeConfigContent(muxName: string, config?: OpenCodeConfig): voi
 export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
   readonly backend = 'tmux' as const;
   private sessions: Map<string, MuxSession> = new Map();
+  private readonly tmuxSocket = resolveConfiguredTmuxSocket();
   private statsInterval: NodeJS.Timeout | null = null;
   private mouseSyncInterval: NodeJS.Timeout | null = null;
   /** Track last-known pane count per session to avoid unnecessary tmux set-option calls */
@@ -351,6 +399,15 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     }
   }
 
+  /** The dedicated tmux socket all Codeman sessions live on (see {@link TerminalMultiplexer.muxSocket}). */
+  get muxSocket(): string {
+    return this.tmuxSocket;
+  }
+
+  private tmux(): string {
+    return tmuxCommand(this.tmuxSocket);
+  }
+
   // Load saved sessions from disk (NEVER called in test mode)
   private loadSessions(): void {
     if (IS_TEST_MODE) return;
@@ -360,8 +417,40 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
         const content = readFileSync(MUX_SESSIONS_FILE, 'utf-8');
         const data = JSON.parse(content);
         if (Array.isArray(data)) {
+          // Dedup by muxName: one live tmux session must map to exactly one
+          // tracked entry. A per-session socket-tag mismatch could historically
+          // let the same session be tracked twice — once under its real UUID and
+          // once under a "restored-<id>" placeholder — surfacing as duplicate tabs.
+          // Single-socket unification removed that failure mode; this pass stays
+          // to clean any stale duplicates already on disk. Keep the real (UUID)
+          // entry and drop placeholder twins.
+          let dropped = 0;
+          const keptByMuxName = new Map<string, string>(); // muxName -> kept sessionId
           for (const session of data) {
+            // Strip the obsolete per-session tmuxSocket tag (now a process-wide
+            // constant). Left in place it would be written back by saveSessions()
+            // and linger on disk as a zombie field forever.
+            delete (session as { tmuxSocket?: unknown }).tmuxSocket;
+            const muxName: string | undefined = session.muxName;
+            const priorId = muxName ? keptByMuxName.get(muxName) : undefined;
+            if (priorId) {
+              const incomingIsPlaceholder = String(session.sessionId).startsWith('restored-');
+              const priorIsPlaceholder = priorId.startsWith('restored-');
+              // Drop the incoming unless it's the real twin of a placeholder we kept.
+              if (incomingIsPlaceholder || !priorIsPlaceholder) {
+                dropped++;
+                continue;
+              }
+              this.sessions.delete(priorId);
+              dropped++;
+            }
             this.sessions.set(session.sessionId, session);
+            if (muxName) keptByMuxName.set(muxName, session.sessionId);
+          }
+          // Persist the cleaned list so the stale duplicates don't reload.
+          if (dropped > 0) {
+            console.log(`[TmuxManager] Dropped ${dropped} duplicate mux session record(s) on load`);
+            this.saveSessions();
           }
         }
       }
@@ -438,7 +527,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
         continue;
       }
       try {
-        execSync(`tmux setenv -t ${shellescape(muxName)} ${key} ${shellescape(value)}`, {
+        execSync(`${this.tmux()} setenv -t ${shellescape(muxName)} ${key} ${shellescape(value)}`, {
           timeout: EXEC_TIMEOUT_MS,
           stdio: ['pipe', 'pipe', 'pipe'],
         });
@@ -471,8 +560,9 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
    * (not visible in ps output or tmux history, inherited by panes).
    */
   private _configureOpenCode(muxName: string, openCodeConfig?: OpenCodeConfig): void {
-    setOpenCodeEnvVars(muxName);
+    const tmuxCmd = this.tmux();
-    setOpenCodeConfigContent(muxName, openCodeConfig);
+    setOpenCodeEnvVars(tmuxCmd, muxName);
+    setOpenCodeConfigContent(tmuxCmd, muxName, openCodeConfig);
   }
 
   /**
@@ -545,7 +635,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
 
     try {
       // Build the full command to run inside tmux
-      const fullCmd = `${pathExport}${envExportsStr} && ${cmd}`;
+      const fullCmd = `${buildNofileLimitCommand()} && ${pathExport}${envExportsStr} && ${cmd}`;
 
       // Create tmux session in three steps to handle cold-start (no server running)
       // and avoid the race where the command exits before remain-on-exit is set:
@@ -556,7 +646,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       // (Production uses systemd which has a clean env, but dev/test may be nested.)
       const cleanEnv = { ...process.env };
       delete cleanEnv.TMUX;
-      execSync(`tmux new-session -ds "${muxName}" -c "${workingDir}"`, {
+      execSync(`${this.tmux()} new-session -ds "${muxName}" -c "${workingDir}"`, {
         cwd: workingDir,
         timeout: EXEC_TIMEOUT_MS,
         stdio: 'ignore',
@@ -565,7 +655,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
 
       // Set remain-on-exit now that the server is running — must be before respawn-pane
       try {
-        execSync(`tmux set-option -t "${muxName}" remain-on-exit on`, {
+        execSync(`${this.tmux()} set-option -t "${muxName}" remain-on-exit on`, {
           timeout: EXEC_TIMEOUT_MS,
           stdio: 'ignore',
         });
@@ -584,7 +674,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       this.applyEnvOverrides(muxName, envOverrides);
 
       // Replace the shell with the actual command (no echo in terminal)
-      execSync(`tmux respawn-pane -k -t "${muxName}" bash -c ${JSON.stringify(fullCmd)}`, {
+      execSync(`${this.tmux()} respawn-pane -k -t "${muxName}" bash -c ${JSON.stringify(fullCmd)}`, {
         timeout: EXEC_TIMEOUT_MS,
         stdio: 'ignore',
       });
@@ -598,20 +688,20 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       // It gets enabled dynamically when panes are split (agent teams).
       const configPromises: Promise<void>[] = [
         // Disable tmux status bar — Codeman's web UI provides session info
-        execAsync(`tmux set-option -t "${muxName}" status off`, { timeout: EXEC_TIMEOUT_MS })
+        execAsync(`${this.tmux()} set-option -t "${muxName}" status off`, { timeout: EXEC_TIMEOUT_MS })
           .then(() => {})
           .catch(() => {
             /* Non-critical — session still works with status bar */
           }),
         // Override global remain-on-exit with session-level setting
-        execAsync(`tmux set-option -t "${muxName}" remain-on-exit on`, { timeout: EXEC_TIMEOUT_MS })
+        execAsync(`${this.tmux()} set-option -t "${muxName}" remain-on-exit on`, { timeout: EXEC_TIMEOUT_MS })
           .then(() => {})
           .catch(() => {
             /* Already set globally as fallback */
           }),
         // Raise tmux scrollback from its 2000-line default so re-attach preserves
         // more context. Matches the xterm-side default in constants.js.
-        execAsync(`tmux set-option -t "${muxName}" history-limit 50000`, { timeout: EXEC_TIMEOUT_MS })
+        execAsync(`${this.tmux()} set-option -t "${muxName}" history-limit 50000`, { timeout: EXEC_TIMEOUT_MS })
           .then(() => {})
           .catch(() => {
             /* Non-critical — falls back to tmux default */
@@ -621,7 +711,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       // Enable 24-bit true color passthrough — server-wide, set once per lifetime
       if (!this.trueColorConfigured) {
         configPromises.push(
-          execAsync(`tmux set-option -sa terminal-overrides ",*:Tc"`, { timeout: EXEC_TIMEOUT_MS })
+          execAsync(`${this.tmux()} set-option -sa terminal-overrides ",*:Tc"`, { timeout: EXEC_TIMEOUT_MS })
             .then(() => {
               this.trueColorConfigured = true;
             })
@@ -678,7 +768,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     }
 
     try {
-      const output = execSync(`tmux display-message -t "${muxName}" -p '#{pane_pid}'`, {
+      const output = execSync(`${this.tmux()} display-message -t "${muxName}" -p '#{pane_pid}'`, {
         encoding: 'utf-8',
         timeout: EXEC_TIMEOUT_MS,
       }).trim();
@@ -704,7 +794,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     if (IS_TEST_MODE) return false;
     if (!isValidMuxName(muxName)) return false;
     try {
-      const output = execSync(`tmux display-message -t "${muxName}" -p '#{pane_dead}'`, {
+      const output = execSync(`${this.tmux()} display-message -t "${muxName}" -p '#{pane_dead}'`, {
         encoding: 'utf-8',
         timeout: EXEC_TIMEOUT_MS,
       }).trim();
@@ -754,7 +844,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     });
     const config = niceConfig || DEFAULT_NICE_CONFIG;
     const cmd = wrapWithNice(baseCmd, config);
-    const fullCmd = `${pathExport}${envExportsStr} && ${cmd}`;
+    const fullCmd = `${buildNofileLimitCommand()} && ${pathExport}${envExportsStr} && ${cmd}`;
 
     try {
       // For OpenCode: set sensitive env vars via tmux setenv before respawn
@@ -765,7 +855,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       // Re-apply user env overrides before respawn so the new shell inherits them.
       this.applyEnvOverrides(muxName, envOverrides);
 
-      await execAsync(`tmux respawn-pane -k -t "${muxName}" bash -c ${JSON.stringify(fullCmd)}`, {
+      await execAsync(`${this.tmux()} respawn-pane -k -t "${muxName}" bash -c ${JSON.stringify(fullCmd)}`, {
         timeout: EXEC_TIMEOUT_MS,
       });
       // Wait for the respawned process to start
@@ -783,7 +873,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     if (IS_TEST_MODE) return false;
 
     try {
-      execSync(`tmux has-session -t "${muxName}" 2>/dev/null`, {
+      execSync(`${this.tmux()} has-session -t "${muxName}" 2>/dev/null`, {
         encoding: 'utf-8',
         timeout: EXEC_TIMEOUT_MS,
       });
@@ -923,7 +1013,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
 
     // Strategy 3: Kill tmux session by name
     try {
-      execSync(`tmux kill-session -t "${session.muxName}" 2>/dev/null`, {
+      execSync(`${this.tmux()} kill-session -t "${session.muxName}" 2>/dev/null`, {
         timeout: EXEC_TIMEOUT_MS,
       });
     } catch {
@@ -988,26 +1078,28 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     const dead: string[] = [];
     const discovered: string[] = [];
 
-    // Batch: single tmux call to get all session names + pane PIDs (replaces N per-session subprocess calls)
+    // Single batched query against the one socket Codeman owns. With a single
-    let activeSessions = new Map<string, number>();
+    // socket a session's location is a constant, so there is no per-session
+    // socket tag to reconcile and no cross-socket ambiguity that could mark a
+    // live session dead (the root cause of vanished/duplicate tabs).
+    let active: Map<string, number>;
     try {
-      const output = execSync(`tmux list-panes -a -F '${PANE_LIST_FORMAT}' 2>/dev/null || true`, {
+      const output = execSync(`${this.tmux()} list-panes -a -F '${PANE_LIST_FORMAT}' 2>/dev/null || true`, {
         encoding: 'utf-8',
         timeout: EXEC_TIMEOUT_MS,
       }).trim();
-      activeSessions = parsePaneList(output);
+      active = parsePaneList(output);
     } catch (err) {
       console.error('[TmuxManager] Failed to list tmux panes:', err);
+      active = new Map();
     }
 
-    // Check known sessions against the batch result (O(1) map lookup instead of subprocess per session)
+    // Check tracked sessions against the live pane list.
     for (const [sessionId, session] of this.sessions) {
-      const pid = activeSessions.get(session.muxName);
+      const pid = active.get(session.muxName);
       if (pid !== undefined) {
         alive.push(sessionId);
-        if (pid !== session.pid) {
+        if (pid !== session.pid) session.pid = pid;
-          session.pid = pid;
-        }
       } else {
         dead.push(sessionId);
         this.sessions.delete(sessionId);
@@ -1015,13 +1107,15 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       }
     }
 
-    // Discover unknown codeman/claudeman sessions from the same batch result
+    // Discover untracked codeman/claudeman sessions on our socket. Dedup by
+    // muxName (globally unique) so a name we already track never spawns a
+    // second "Restored:" entry.
     const knownMuxNames = new Set<string>();
     for (const session of this.sessions.values()) {
       knownMuxNames.add(session.muxName);
     }
 
-    for (const [sessionName, pid] of activeSessions) {
+    for (const [sessionName, pid] of active) {
       if (!sessionName.startsWith('codeman-') && !sessionName.startsWith('claudeman-')) continue;
       if (knownMuxNames.has(sessionName)) continue;
 
@@ -1038,6 +1132,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
         name: `Restored: ${sessionName}`,
       };
       this.sessions.set(sessionId, session);
+      knownMuxNames.add(sessionName);
       discovered.push(sessionId);
       console.log(`[TmuxManager] Discovered unknown tmux session: ${sessionName} (PID ${pid})`);
     }
@@ -1345,21 +1440,21 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
         // Ink (Claude CLI's terminal framework) needs them split — sending both in a
         // single tmux invocation (via \;) causes Ink to interpret Enter as a newline
         // character in the input buffer rather than as form submission.
-        await execAsync(`tmux send-keys -t "${session.muxName}" -l ${shellescape(textPart)}`, {
+        await execAsync(`${this.tmux()} send-keys -t "${session.muxName}" -l ${shellescape(textPart)}`, {
           timeout: EXEC_TIMEOUT_MS,
         });
         await new Promise((resolve) => setTimeout(resolve, 50));
-        await execAsync(`tmux send-keys -t "${session.muxName}" Enter`, {
+        await execAsync(`${this.tmux()} send-keys -t "${session.muxName}" Enter`, {
           timeout: EXEC_TIMEOUT_MS,
         });
       } else if (textPart) {
         // Text only, no Enter
-        await execAsync(`tmux send-keys -t "${session.muxName}" -l ${shellescape(textPart)}`, {
+        await execAsync(`${this.tmux()} send-keys -t "${session.muxName}" -l ${shellescape(textPart)}`, {
           timeout: EXEC_TIMEOUT_MS,
         });
       } else if (hasCarriageReturn) {
         // Enter only
-        await execAsync(`tmux send-keys -t "${session.muxName}" Enter`, {
+        await execAsync(`${this.tmux()} send-keys -t "${session.muxName}" Enter`, {
           timeout: EXEC_TIMEOUT_MS,
         });
       }
@@ -1386,7 +1481,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     }
 
     try {
-      execSync(`tmux set-option -t "${muxName}" mouse on`, {
+      execSync(`${this.tmux()} set-option -t "${muxName}" mouse on`, {
         encoding: 'utf-8',
         timeout: EXEC_TIMEOUT_MS,
       });
@@ -1410,7 +1505,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     }
 
     try {
-      execSync(`tmux set-option -t "${muxName}" mouse off`, {
+      execSync(`${this.tmux()} set-option -t "${muxName}" mouse off`, {
         encoding: 'utf-8',
         timeout: EXEC_TIMEOUT_MS,
       });
@@ -1450,7 +1545,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
 
     try {
       const output = execSync(
-        `tmux list-panes -t "${muxName}" -F '#{pane_id}:#{pane_index}:#{pane_pid}:#{pane_width}:#{pane_height}'`,
+        `${this.tmux()} list-panes -t "${muxName}" -F '#{pane_id}:#{pane_index}:#{pane_pid}:#{pane_width}:#{pane_height}'`,
         { encoding: 'utf-8', timeout: EXEC_TIMEOUT_MS }
       ).trim();
 
@@ -1489,27 +1584,28 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
 
     // Build target: sessionName.paneId (e.g., "codeman-abc12345.%1")
     const target = paneTarget.startsWith('%') ? `${muxName}.${paneTarget}` : `${muxName}.%${paneTarget}`;
+    const tmux = this.tmux();
 
     try {
       const hasCarriageReturn = input.includes('\r');
       const textPart = input.replace(/\r/g, '').replace(/\n/g, '').trimEnd();
 
       if (textPart && hasCarriageReturn) {
-        execSync(`tmux send-keys -t ${shellescape(target)} -l ${shellescape(textPart)}`, {
+        execSync(`${tmux} send-keys -t ${shellescape(target)} -l ${shellescape(textPart)}`, {
           encoding: 'utf-8',
           timeout: EXEC_TIMEOUT_MS,
         });
-        execSync(`tmux send-keys -t ${shellescape(target)} Enter`, {
+        execSync(`${tmux} send-keys -t ${shellescape(target)} Enter`, {
           encoding: 'utf-8',
           timeout: EXEC_TIMEOUT_MS,
         });
       } else if (textPart) {
-        execSync(`tmux send-keys -t ${shellescape(target)} -l ${shellescape(textPart)}`, {
+        execSync(`${tmux} send-keys -t ${shellescape(target)} -l ${shellescape(textPart)}`, {
           encoding: 'utf-8',
           timeout: EXEC_TIMEOUT_MS,
         });
       } else if (hasCarriageReturn) {
-        execSync(`tmux send-keys -t ${shellescape(target)} Enter`, {
+        execSync(`${tmux} send-keys -t ${shellescape(target)} Enter`, {
           encoding: 'utf-8',
           timeout: EXEC_TIMEOUT_MS,
         });
@@ -1540,7 +1636,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     const target = paneTarget.startsWith('%') ? `${muxName}.${paneTarget}` : `${muxName}.%${paneTarget}`;
 
     try {
-      return execSync(`tmux capture-pane -p -e -t ${shellescape(target)} -S -5000`, {
+      return execSync(`${this.tmux()} capture-pane -p -e -t ${shellescape(target)} -S -5000`, {
         encoding: 'utf-8',
         timeout: EXEC_TIMEOUT_MS,
       });
@@ -1572,7 +1668,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     const target = paneTarget.startsWith('%') ? `${muxName}.${paneTarget}` : `${muxName}.%${paneTarget}`;
 
     try {
-      execSync(`tmux pipe-pane -O -t ${shellescape(target)} ${shellescape('cat >> ' + outputFile)}`, {
+      execSync(`${this.tmux()} pipe-pane -O -t ${shellescape(target)} ${shellescape('cat >> ' + outputFile)}`, {
         encoding: 'utf-8',
         timeout: EXEC_TIMEOUT_MS,
       });
@@ -1600,7 +1696,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     const target = paneTarget.startsWith('%') ? `${muxName}.${paneTarget}` : `${muxName}.%${paneTarget}`;
 
     try {
-      execSync(`tmux pipe-pane -t ${shellescape(target)}`, {
+      execSync(`${this.tmux()} pipe-pane -t ${shellescape(target)}`, {
         encoding: 'utf-8',
         timeout: EXEC_TIMEOUT_MS,
       });
@@ -1616,7 +1712,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
   }
 
   getAttachArgs(muxName: string): string[] {
-    return ['attach-session', '-t', muxName];
+    return ['-L', this.tmuxSocket, 'attach-session', '-t', muxName];
   }
 
   isAvailable(): boolean {

src/web/routes/session-routes.ts

@@ -652,11 +652,18 @@ export function registerSessionRoutes(
     }
 
     try {
+      // Route through the dedicated Codeman socket — bare `tmux` would target the
+      // user's default server and never find this session (same #80 regression class).
       await new Promise<void>((resolve, reject) => {
-        execFile('tmux', ['send-keys', '-H', '-t', muxName, ...hex], { timeout: 5000 }, (err) => {
+        execFile(
-          if (err) reject(err);
+          'tmux',
-          else resolve();
+          ['-L', ctx.mux.muxSocket, 'send-keys', '-H', '-t', muxName, ...hex],
-        });
+          { timeout: 5000 },
+          (err) => {
+            if (err) reject(err);
+            else resolve();
+          }
+        );
       });
     } catch (err) {
       console.error('[Server] send-key failed:', err);

test/mocks/mock-route-context.ts

@@ -90,6 +90,7 @@ export function createMockRouteContext(options?: { sessionId?: string }) {
 
     // -- InfraPort --
     mux: {
+      muxSocket: 'codeman',
       createSession: vi.fn(),
       killSession: vi.fn(),
       listSessions: vi.fn(() => []),

test/routes/session-routes.test.ts

@@ -7,6 +7,14 @@
 
 import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
 import { createRouteTestHarness, type RouteTestHarness } from './_route-test-utils.js';
+
+// Mock execFile so the send-key route's `tmux` invocation is observable (not run for real).
+const { execFile } = vi.hoisted(() => ({ execFile: vi.fn() }));
+vi.mock('node:child_process', async (orig) => {
+  const actual = await orig<typeof import('node:child_process')>();
+  return { ...actual, execFile };
+});
+
 import { registerSessionRoutes } from '../../src/web/routes/session-routes.js';
 
 describe('session-routes', () => {
@@ -20,6 +28,44 @@ describe('session-routes', () => {
     await harness.app.close();
   });
 
+  // ========== POST /api/sessions/:id/send-key ==========
+
+  describe('POST /api/sessions/:id/send-key', () => {
+    it('routes tmux send-keys through the dedicated Codeman socket (-L)', async () => {
+      // Regression guard: bare `tmux` would hit the user's default server and never
+      // find a session that lives only on the Codeman socket (#80 regression class).
+      execFile.mockReset();
+      execFile.mockImplementation((_bin: string, _argv: string[], _opts: unknown, cb: (e: Error | null) => void) =>
+        cb(null)
+      );
+
+      const res = await harness.app.inject({
+        method: 'POST',
+        url: '/api/sessions/test-session-1/send-key',
+        payload: { key: 'S-Enter' },
+      });
+
+      expect(res.statusCode).toBe(200);
+      expect(execFile).toHaveBeenCalledTimes(1);
+      const [bin, argv] = execFile.mock.calls[0];
+      expect(bin).toBe('tmux');
+      expect((argv as string[]).slice(0, 2)).toEqual(['-L', 'codeman']);
+      expect(argv).toContain('send-keys');
+      expect(argv).toContain('-H');
+    });
+
+    it('rejects keys outside the hex allowlist without invoking tmux', async () => {
+      execFile.mockReset();
+      const res = await harness.app.inject({
+        method: 'POST',
+        url: '/api/sessions/test-session-1/send-key',
+        payload: { key: 'rm -rf' },
+      });
+      expect(JSON.parse(res.body).success).toBe(false);
+      expect(execFile).not.toHaveBeenCalled();
+    });
+  });
+
   // ========== GET /api/sessions ==========
 
   describe('GET /api/sessions', () => {

test/tmux-manager.test.ts

@@ -77,9 +77,24 @@ describe('TmuxManager (unit)', () => {
   });
 
   describe('getAttachArgs', () => {
-    it('should return attach-session args', () => {
+    it('should attach every session through the dedicated Codeman socket', () => {
       const args = manager.getAttachArgs('codeman-abc12345');
-      expect(args).toEqual(['attach-session', '-t', 'codeman-abc12345']);
+      expect(args).toEqual(['-L', 'codeman', 'attach-session', '-t', 'codeman-abc12345']);
+    });
+
+    it('should attach registered sessions on the same dedicated socket (no per-session socket)', () => {
+      manager.registerSession({
+        sessionId: 'some-session',
+        muxName: 'codeman-abc12345',
+        pid: 12345,
+        createdAt: Date.now(),
+        workingDir: '/tmp',
+        mode: 'claude',
+        attached: false,
+      });
+
+      const args = manager.getAttachArgs('codeman-abc12345');
+      expect(args).toEqual(['-L', 'codeman', 'attach-session', '-t', 'codeman-abc12345']);
     });
   });
 

test/tmux-window-size-query.test.ts

@@ -8,7 +8,8 @@
  * the next frame — visible flicker and one lost repaint of scrollback.
  *
  * The fix queries tmux for the actual window geometry first via
- * `tmux display -t <name> -p '#{window_width} #{window_height}'`. We cover:
+ * `tmux -L <socket> display -t <name> -p '#{window_width} #{window_height}'`
+ * (the `-L <socket>` targets the isolated Codeman socket). We cover:
  *   - Happy path: tmux reports valid geometry → those numbers are used.
  *   - Browser-resize-between-attaches: tmux reports a non-default size
  *     (because a prior client resized it) → the helper picks that up.
@@ -49,7 +50,7 @@ beforeEach(() => {
 describe('queryTmuxWindowSize — happy path', () => {
   it('returns the geometry tmux reports', () => {
     execFileSync.mockReturnValue('200 50\n');
-    expect(queryTmuxWindowSize('codeman-abc')).toEqual({ cols: 200, rows: 50 });
+    expect(queryTmuxWindowSize('codeman-abc', 'codeman')).toEqual({ cols: 200, rows: 50 });
   });
 
   it('picks up a non-default size left behind by a prior client (browser-resize-between-attaches)', () => {
@@ -57,12 +58,12 @@ describe('queryTmuxWindowSize — happy path', () => {
     // tmux keeps the last-attached geometry. Client B re-attaches and should spawn
     // its PTY at 220x60, not 120x40 — that's the whole point of #80.
     execFileSync.mockReturnValue('220 60');
-    expect(queryTmuxWindowSize('codeman-abc')).toEqual({ cols: 220, rows: 60 });
+    expect(queryTmuxWindowSize('codeman-abc', 'codeman')).toEqual({ cols: 220, rows: 60 });
   });
 
   it('tolerates trailing whitespace and newlines in tmux output', () => {
     execFileSync.mockReturnValue('  180 45  \n\n');
-    expect(queryTmuxWindowSize('codeman-abc')).toEqual({ cols: 180, rows: 45 });
+    expect(queryTmuxWindowSize('codeman-abc', 'codeman')).toEqual({ cols: 180, rows: 45 });
   });
 });
 
@@ -75,7 +76,7 @@ describe('queryTmuxWindowSize — fallback paths', () => {
       err.status = 1;
       throw err;
     });
-    expect(queryTmuxWindowSize('bogus')).toEqual(DEFAULT);
+    expect(queryTmuxWindowSize('bogus', 'codeman')).toEqual(DEFAULT);
   });
 
   it('falls back when tmux dies between query and parse (ETIMEDOUT / ENOENT)', () => {
@@ -85,63 +86,65 @@ describe('queryTmuxWindowSize — fallback paths', () => {
       err.code = 'ETIMEDOUT';
       throw err;
     });
-    expect(queryTmuxWindowSize('codeman-abc')).toEqual(DEFAULT);
+    expect(queryTmuxWindowSize('codeman-abc', 'codeman')).toEqual(DEFAULT);
   });
 
   it('falls back when tmux returns empty output', () => {
     execFileSync.mockReturnValue('');
-    expect(queryTmuxWindowSize('codeman-abc')).toEqual(DEFAULT);
+    expect(queryTmuxWindowSize('codeman-abc', 'codeman')).toEqual(DEFAULT);
   });
 
   it('falls back when tmux returns whitespace-only output', () => {
     execFileSync.mockReturnValue('   \n');
-    expect(queryTmuxWindowSize('codeman-abc')).toEqual(DEFAULT);
+    expect(queryTmuxWindowSize('codeman-abc', 'codeman')).toEqual(DEFAULT);
   });
 
   it('falls back when tmux returns non-numeric output', () => {
     execFileSync.mockReturnValue('not a size\n');
-    expect(queryTmuxWindowSize('codeman-abc')).toEqual(DEFAULT);
+    expect(queryTmuxWindowSize('codeman-abc', 'codeman')).toEqual(DEFAULT);
   });
 
   it('falls back when only one dimension is present', () => {
     execFileSync.mockReturnValue('200\n');
-    expect(queryTmuxWindowSize('codeman-abc')).toEqual(DEFAULT);
+    expect(queryTmuxWindowSize('codeman-abc', 'codeman')).toEqual(DEFAULT);
   });
 
   it('falls back when a dimension is zero (degenerate geometry)', () => {
     // tmux reporting `0` would crash node-pty downstream — must not propagate.
     execFileSync.mockReturnValue('0 40\n');
-    expect(queryTmuxWindowSize('codeman-abc')).toEqual(DEFAULT);
+    expect(queryTmuxWindowSize('codeman-abc', 'codeman')).toEqual(DEFAULT);
     execFileSync.mockReturnValue('120 0\n');
-    expect(queryTmuxWindowSize('codeman-abc')).toEqual(DEFAULT);
+    expect(queryTmuxWindowSize('codeman-abc', 'codeman')).toEqual(DEFAULT);
   });
 
   it('falls back when a dimension is negative', () => {
     execFileSync.mockReturnValue('-200 -50\n');
-    expect(queryTmuxWindowSize('codeman-abc')).toEqual(DEFAULT);
+    expect(queryTmuxWindowSize('codeman-abc', 'codeman')).toEqual(DEFAULT);
   });
 
   it('falls back when tmux returns NaN-producing tokens', () => {
     execFileSync.mockReturnValue('abc def\n');
-    expect(queryTmuxWindowSize('codeman-abc')).toEqual(DEFAULT);
+    expect(queryTmuxWindowSize('codeman-abc', 'codeman')).toEqual(DEFAULT);
   });
 });
 
 describe('queryTmuxWindowSize — call shape', () => {
-  it('invokes tmux with display -t <name> -p ... via argv (not a shell)', () => {
+  it('invokes tmux on the dedicated socket via argv (not a shell)', () => {
     execFileSync.mockReturnValue('120 40\n');
-    queryTmuxWindowSize('codeman-abc');
+    queryTmuxWindowSize('codeman-abc', 'codeman');
     expect(execFileSync).toHaveBeenCalledTimes(1);
     const [bin, argv, opts] = execFileSync.mock.calls[0];
     expect(bin).toBe('tmux');
-    expect(argv).toEqual(['display', '-t', 'codeman-abc', '-p', '#{window_width} #{window_height}']);
+    // `-L <socket>` MUST lead: querying the default server would never find a
+    // session that lives on the isolated Codeman socket (the #80 regression).
+    expect(argv).toEqual(['-L', 'codeman', 'display', '-t', 'codeman-abc', '-p', '#{window_width} #{window_height}']);
     // execFileSync — not execSync — so muxName is never substituted into a shell string.
     expect(opts).toMatchObject({ encoding: 'utf8' });
   });
 
   it('uses a bounded timeout so a hung tmux server cannot block startup forever', () => {
     execFileSync.mockReturnValue('120 40\n');
-    queryTmuxWindowSize('codeman-abc');
+    queryTmuxWindowSize('codeman-abc', 'codeman');
     const [, , opts] = execFileSync.mock.calls[0];
     // Whatever the exact constant, the contract is: ≤5s so the user-visible
     // attach path can't hang on a stuck tmux server.
@@ -152,12 +155,12 @@ describe('queryTmuxWindowSize — call shape', () => {
 
   it('passes a muxName that looks like a tmux flag as an argv element (no option injection)', () => {
     execFileSync.mockReturnValue('120 40\n');
-    queryTmuxWindowSize('-x 1 -y 1; rm -rf');
+    queryTmuxWindowSize('-x 1 -y 1; rm -rf', 'codeman');
     const [, argv] = execFileSync.mock.calls[0];
-    // The whole "name" lives in a single argv slot, so tmux interprets it as a
+    // The whole "name" lives in a single argv slot (index 4, after `-L codeman
-    // target session name, not as additional flags. The `-t` flag preceding it
+    // display -t`), so tmux interprets it as a target session name, not as
-    // pins it as the target argument.
+    // additional flags. The `-t` flag preceding it pins it as the target.
-    expect(argv?.[2]).toBe('-x 1 -y 1; rm -rf');
+    expect(argv?.[4]).toBe('-x 1 -y 1; rm -rf');
     expect((argv as string[]).indexOf('-x')).toBe(-1);
   });
 });